Magnet robot crawler

ABSTRACT

A magnetic robot includes a chassis and at least one track assembly associated with the chassis. The track assembly has a linear series of non-circulating magnet modules displaceably mounted with respect to the chassis. A driven track circulates about the magnet modules and travels on guide portions of the magnet modules.

GOVERNMENT RIGHTS

Certain aspects of this invention were developed under U.S. GovernmentOffice of Naval Research contract No. N00014-08-C-0408. The U.S.Government may have certain rights in the subject invention.

FIELD OF THE INVENTION

The invention relates to magnet robotic crawlers and similar systems.

BACKGROUND OF THE INVENTION

Magnetic robot crawlers configured to traverse ferrous surfaces such asconstruction steel, tanks, piping, pier pilings, or hull of a ship havebeen designed. Some crawlers use electromagnets (see for example U.S.Pat. No. 4,890,567); others use permanent magnets as disclosed in U.S.Pat. Nos. 3,682,265; 3,777,834; 5,285,601; and 5,894,901 allincorporated herein by this reference.

U.S. Pat. No. 5,285,601 shows a robot with permanent magnet tracktreads. U.S. Pat. No. 5,894,901 discloses a complex design withcirculating permanent magnets in the track. U.S. Pat. No. 3,682,265shows a v-belt track below fixed permanent magnets.

Some structures include discontinuities such as weld beads up to 0.5inches tall as well as other obstacles. If a ferrous surface issubmerged and exposed to currents of 15 knots, in one example, the dragand lifting forces on the robot can be substantial. If the robot drivesover a discontinuity, it may pitch outwardly from the surface and can belifted off the surface due to the drag and/or lift forces resulting in aloss of the robot especially if it is not tethered to the surface.

Since autonomous operation is desirable and since such a robot can beexpensive, it is desirable to avoid the loss of the robot. If rotatingmagnetic treads are used, energy must be used to lift the treads off thehull during revolution of the tracks which can affect battery life inthe case of an autonomous battery powered robot.

SUMMARY OF THE INVENTION

In one aspect and in one preferred example in accordance with theinvention, a robot is provided which is able to traverse discontinuitiesand still remain securely attached to the surface. In one example, afairly large, low profile robot includes cameras and the like and alsocompliant permanent magnet track assemblies which enable the robot toremain on the ferrous surface despite surface discontinuities such asweld beads and large drag and lift forces. In one preferred version, thepermanent magnets do not circulate extending battery life.

Featured is a magnetic robot including a chassis and at least one trackassembly associated with, the chassis. The track assembly includes aplurality of magnet modules displaceably mounted with respect to thechassis and including a track guide portion. A driven track is disposedabout the magnet modules and travels on the magnet module guideportions.

In one design, the magnet modules further include guide walls for thetrack. In one example, the magnet modules include at least one permanentmagnet sandwiched between a flux return backer and an intensifier polepiece. Preferably, there are two adjacent permanent magnets havingopposite polarity and the intensifier pole piece converges from a broadportion to a narrower distal portion. There may be a protective shoeover the intensifier pole piece distal narrower portion.

The chassis may include a slotted frame for the magnet modules and, inthis design, the magnet modules include a head portion received in theslotted frame. Further included may be a spring between the slottedframe and the head portion. One version of a slotted frame includes atop guide rail for the track.

The robot track may include slats coupled to a chain. In one example,the slats include discontinuities to prevent magnetic flux shunting andspaced bottom angled ribs for traction. Adjacent slats may haveoppositely angled ribs in a repeating herringbone pattern. Also, theslat bottom ends can be angled upwardly and outwardly.

In some designs, one or more magnet module guide portions include atleast one force sensor. Also, a fairing may have a lift reducing profilefore and aft of the robot.

One track assembly comprises a linear series of non-circulating magnetmodules displaceably mounted with respect to a frame, each magnet moduleincluding a guide portion, and a track about the magnet modules andincluding a guided portion traveling with respect to the magnet modulesand guided by the magnet module guide portions. The guided portion ofthe track may include a chain and a magnet module guide portion mayinclude a chain rail.

Also featured is a magnet track assembly comprising a series ofnon-circulating adjacent magnet modules extending in a first directionand displaceably mounted in a frame in a second direction and a trackextending about and circulating with respect to the series of magnetmodules.

Also featured is a method of operating a robot, the method comprisingdisplaceably mounting a plurality of non-circulating magnet modules withrespect to a robot chassis and driving an endless belt about the magnetmodules and guided by the magnet modules.

The subject invention, however, in other embodiments, need not achieveall these objectives and the claims hereof should not be limited tostructures or methods capable of achieving these objectives.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Other objects, features and advantages will occur to those skilled inthe art from the following description of a preferred embodiment and theaccompanying drawings, in which:

FIG. 1A is a schematic three dimensional rear view of an example of arobot in accordance with the invention;

FIG. 1B is a schematic three dimension front view of the robot of FIG.1B;

FIG. 2 is a schematic three dimensional view showing a robot inaccordance with FIGS. 1A and 1B with the fairing removed;

FIG. 3 is a schematic three dimensional side view of a magneticsubassembly for the tracks of the robot shown in FIG. 2;

FIG. 4 is a schematic three dimensional illustrative view showingportions of the subassembly of FIG. 3;

FIG. 5 is a schematic three dimensional partially cutaway view of amagnet module component of the subassembly shown in FIG. 4;

FIG. 6 is a schematic cross sectional view of the magnet module shown inFIG. 5;

FIG. 7 is a schematic side view of the robot of FIGS. 1-2 traversing adiscontinuity;

FIG. 8A is a highly schematic cross sectional diagram showing anothermagnet module in accordance with the invention biasing the robot trackon a ferromagnetic surface;

FIG. 8B schematically depicts how the magnet module of 8A displacesupwardly in the presence of a discontinuity on the surface of theferromagnetic surface;

FIG. 9 is a schematic cross sectional front view showing the circularmagnet flux path for the specific design of a module as depicted inFIGS. 5-6;

FIG. 10 is a schematic view showing the bottom surface of a track slatin accordance with one particular example of the invention; and

FIG. 11 is a schematic cross sectional view showing an example of achain guide rail with one or more strain gages in accordance withexamples of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Aside from the preferred embodiment or embodiments disclosed below, thisinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Thus, it is to be understood that theinvention is not limited in its application to the details ofconstruction and the arrangements of components set forth in thefollowing description or illustrated in the drawings. If only oneembodiment is described herein, the claims hereof are not to be limitedto that embodiment. Moreover, the claims hereof are not to be readrestrictively unless there is clear and convincing evidence manifestinga certain exclusion, restriction, or disclaimer.

FIGS. 1A and 1B show an example of a crawler robot 10 which is 6.5inches tall and 39 inches by 41 inches in area and with inspectioncameras 12 a-12 d and track assemblies 14 a and 14 b driving chassis 16which is at least partially surrounded by fairing 18.

FIG. 2 shows the fairing removed and the chassis housing batteries 20 aand 20 b, motors, electronic subassembly 22, and the like. Rearsprockets 26 a and 26 b are motor driven and forward idler sprockets 28a and 28 b are spring loaded to tension track belts 30 a and 30 b loopedover rear driven sprockets 26, forward idler sprockets 28, and about amagnetic subassembly affixed to the chassis on each side thereof.Magnetic subassembly 32 a is shown in FIGS. 2-4.

In one design, a linear series of 7-8 individual magnet modules areincluded in each subassembly 32 a. FIGS. 3-4 show subassembly frame 40with plate 42 fastened to the chassis and plate 44 extending outwardlytherefrom. Top track rail 46 a is on the top of plate 44. Magnet modules50 a, 501), 50 c and the like in a series are displaceably mounted withrespect to the frame 40 and thus the chassis enabling compliance andflexibility for the track assemblies as they encounter discontinuities.The magnet modules do not circulate with the tracks but they aredisplaceable upwards (in the Figures) as discussed below.

In this particular example, each magnet module 50 includes permanentmagnets 60 a and 60 b sandwiched between flux retainer backer 62 andintensifier pole pieces 64 a and 64 b. Adjacent permanent magnets 60 aand 60 b have opposite polarity, for example, the top face of 60 a issouth while the top face of magnet 60 b is north.

Attached to backer 62 in this particular example is T-shaped head piece70 received in slotted chassis frame portion 72 defined by plate 44 andinwardly angled members 74 a and 74 b which form spaced shelves or stops76 a and 76 b for the top of T-shaped head 70 above neck portion 69which is attached to backer 62. Spring 80 between head 70 and plate 44biases the magnet modules downward (in the figure) until rail 46 b hitsroller 92 but allows a magnet module to travel ½ inch or more upwards inthe presence of a discontinuity and/or to rock back and forth as spring80 is compressed and the top of T-shaped head 70 displaces from spacedshelves 76 a and 76 b and travels upwards toward plate 44. The othermodules of the track stay down. Spring 80 is typically set in a counterbore in head piece 70. Other structures for rendering the magnet modulescompliant with respect to the chassis are possible.

In the version shown, the magnet modules further include a guide such asrail 46 b between magnets 60 a and 60 b and between intensifier polepieces 64 a and 64 b. Here, intensifier pole pieces 64 a and 64 bconverge from broad portion 65 a (as shown for pole piece 64 a, FIG. 5)to narrow distal portion 67 a fitted with protective (e.g., bronze) shoe81 a. This opening between intensifier portions 64 a and 64 b alsopreferably includes laterally spaced chain guide wall members 91 a and91 b and depending track rail 46 b. A fastener or the like may extendthrough head piece 70, pole piece 62, and into bottom rail 46 b tofasten all these components together.

In this particular embodiment, driven track belt 30 a includes slats 90a, 90 b, 90 c and the like fastened to chain 92 via chain frame 94. Therollers of the chain (typically two per link) travel on the rails 46 aand 46 b and between chain guide wall members 91 a and 91 b. As shown inFIG. 7, when module 50 a encounters discontinuity 109 on hull 106,module 50 a rises up but the other modules stay down on the hull.

In other embodiments, the track may include a guided travel structureother than a chain and the magnet modules can be configured differentlyfrom the structures shown in FIGS. 4-7. Moreover, all the magnet modulesneed not be configured the same.

For example, FIGS. 8A and 8B show track 100 and magnet module 102displaceable with respect to chassis 104 (or a structure attached to thechassis). When hull 106 discontinuity 108, FIG. 8B is encountered, thismagnet module is displaced upwardly as shown but the other magnetmodules in the series stay down as shown in FIG. 8A close to hull 106enabling the robot to adhere to the hull even in the presence of largedrag and lift forces and discontinuities.

Referring now to the previous embodiment discussed above as an examplein FIGS. 1-7, FIG. 9 shows the magnet flux lines for magnet module 50 ashowing how efficient the flux path is to hull 106. 150-225 lbs. pulloff force per magnet module for a 350 lb robot is preferred enabling therobot to stay attached to a ferrous substrate even in the presence of450 lbs of drag force and 200 lbs of lifting force. In one particularembodiment, the robot crawler is able to navigate on a submerged ferroussurface exposed to currents up to 15 knots over bio-fouling areas and/ordiscrete (small in area) obstacles 0.38-0.50 inches tall such as weldbeads, steps, and the like. The low profile configuration of the robotpresents minimal flow resistance.

Two tracks are preferably used for skid steering and the four camerasdepicted in FIGS. 1A and 1B are used for machine vision. In non-tetheredoperation, control and video signals are transmitted through the water.The tracks preferably exhibit a high surface area contact for goodtraction on a hull and the chain and track slat construction provide forcorrosion resistance, durability, a high coefficient of friction tominimize slipping, and compatibility with the magnetic structure.Stainless steel materials are preferred. The magnetic hold downsubsystem allows the robot to stay low to the surface while going up andover small bumps or steps. Each magnet module preferably has a 0.50 inchvertical range of motion or float. Spring loading of each modulecontrols the overall chassis suspension stiffness while allowing eachmagnet module to move up and down to follow the surface whilemaintaining a constant low crawler attitude to the flow. Positioning themagnets over the rotating tracks reduces the chance that the magnets orpole pieces will get caught on or interfere with crawler movement overobstacles or steps while maintaining a small fixed standoff of themagnet modules over a ferrous surface for less decay of the magnetforce. Most force of the mechanical motion is absorbed by the chainsupport rails 46 b whose height is set for a nominal 0.02 inchesclearance from the protective shoes 80 a and 80 b to the track slat 90,FIG. 4.

FIG. 10 shows one preferred track slat 90 a with holes 120 a and 120 bfor fasteners to affix the slat to the chain frame and alsodiscontinuities (e.g., holes) 122 a and 122 b for minimizing flux “crosstalk” or travel across from one magnet to the other above the ferroussurface which would shunt or short circuit the intended circular pathwhich is over the magnets, through a pole piece and slat portion, intothe ferrous surface, and across the surface and back up as depicted inFIG. 9.

Two magnets per module provide an efficient controlled flux loop. Thesteel backer plate connects the two magnets on top and provides goodmodule structure and provides an efficient flux path on the top of themagnets. The tapered pole pieces under each magnet are shaped tointensify the flux circuit directly through the track slats. Most of thechain parts are non-magnetic to minimize interference with the fluxpattern and the track slats are preferably highly magnetically permeableto maximize transmission of flux through the slats to a steel surface.

Spaced angled ribs 124, FIG. 10 are machined or otherwise formed in thebottom face of the slats for traction. Adjacent slats may haveoppositely angled ribs in a repeating herringbone pattern to resistslipping in all directions and to crush soft attached materials orsubstances such as biomatter. The slat ends are angled as shown in FIG.10 at 126 meaning the top of the slat is longer than the bottom of theslat. This design assists in maneuverability of the robotic crawler asit drives at an angle across an obstruction.

FIG. 11 shows how a track guide rail 46 fore and/or aft portions mayinclude an upwardly curved ski portion 130 for better operation in thecase of a slack in the track chain. The rail structure 134 sandwichedbetween the permanent magnets and the intensifier pole pieces (see FIG.5) can include strain gauges 136 a, 136 b, and the like forming a loadcell used to monitor the hold down force and to adjust the robots' pathof travel and/or behavior accordingly. The load cells can be located,for example, in every other module.

In other designs, fixed magnets can be used underneath the crawlerchassis to increase the hold down force. Also, fairing 18, FIGS. 1A and1B in the front of the robot typically has a short S-curved profile tominimize lift. This profile does increase drag when exposed to currentsbut reduces the “zipper effect” of the robot magnet modules being pulledaway from the ferrous surface one at a time. A medium taper fairingprofile is preferred on the sides of the robot to reduce drag. There issome increased lift due to this profile which is resisted by the magnetmodules discussed above. Known ferrous surface inspection, cleaning,navigation, energy harvesting, and other technologies may beincorporated as well as various behaviors and control algorithms knownto those skilled in the art. In all the various embodiments andversions, it is preferred that the robot be able to traversediscontinuities and still remain securely attached to the surface andthus the compliant permanent magnet modules for the track assemblies,one example of which is disclosed herein, are preferred.

Thus, although specific features of the invention are shown in somedrawings and not in others, this is for convenience only as each featuremay be combined with any or all of the other features in accordance withthe invention. The words “including”, “comprising”, “having”, and “with”as used herein are to be interpreted broadly and comprehensively and arenot limited to any physical interconnection. Moreover, any embodimentsdisclosed in the subject application are not to be taken as the onlypossible embodiments.

In addition, any amendment presented during the prosecution of thepatent application for this patent is not a disclaimer of any claimelement presented in the application as filed: those skilled in the artcannot reasonably be expected to draft a claim that would literallyencompass all possible equivalents, many equivalents will beunforeseeable at the time of the amendment and are beyond a fairinterpretation of what is to be surrendered (if anything), the rationaleunderlying the amendment may bear no more than a tangential relation tomany equivalents, and/or there are many other reasons the applicant cannot be expected to describe certain insubstantial substitutes for anyclaim element amended.

Other embodiments will occur to those skilled in the art and are withinthe following claims.

What is claimed is:
 1. A magnetic robot comprising: a chassis; at leastone track assembly associated with the chassis, the track assemblyincluding: a plurality of magnet modules displaceably mounted withrespect to the chassis and including a track guide portion, the magnetmodules including at least one permanent magnet sandwiched between aflux return backer and an intensifier pole piece; and a driven trackabout the magnet modules travelling on said magnet module guideportions.
 2. The robot of claim 1 in which a magnet module has twoadjacent permanent magnets having opposite polarity.
 3. The robot ofclaim 2 in which the magnet module has intensifier pole piece convergesfrom a broad portion to a narrower distal portion.
 4. The robot of claim3 further including a protective shoe over the intensifier pole piecedistal narrower portion.
 5. The robot of claim 1 in which the chassisincludes a slotted frame for the magnet modules.
 6. The robot of claim 5in which the magnet module includes a head portion received in theslotted frame.
 7. The robot of claim 6 in which further including aspring between the slotted frame and the head portion.
 8. The robot ofclaim 5 in which the slotted frame includes a top guide rail for thetrack.
 9. The robot of claim 1 in which the track includes slats coupledto a chain.
 10. The robot of claim 9 in which the slats includediscontinuities to prevent shunting.
 11. The robot of claim 9 in whichthe slats include spaced bottom ribs for traction.
 12. The robot ofclaim 11 in which said ribs are angled.
 13. The robot of claim 12 inwhich adjacent slats have oppositely angled ribs in a repeatingherringbone pattern.
 14. The robot of claim 9 in which the slat bottomends are angled upwardly and outwardly.
 15. The robot of claim 1 inwhich one or more magnet module guide portions include at least oneforce sensor.
 16. The robot of claim 1 further including a fairinghaving a lift reducing profile fore and aft of the robot.
 17. A magneticrobot comprising: a chassis; a slotted frame attached to the chassisincluding spaced stops; at least one track assembly associated with thechassis, the track assembly including: a plurality of magnet modulesdisplaceably mounted with respect to the chassis slotted frame andincluding a track guide portion and a T-shaped head received in theslotted frame and biased into engagement with the spaced stops of theslotted frame; and a driven track about the magnet modules travelling onsaid magnet module guide portions.
 18. A magnetic robot comprising: achassis including a slotted frame; at least one track assemblyassociated with the chassis, the track assembly including: a pluralityof magnet modules displaceably mounted with respect to the chassis andincluding a track guide portion and a head portion received in theslotted frame of the chassis; and a driven track about the magnetmodules travelling on said magnet module guide portions.
 19. The robotof claim 18 in which the magnet modules further include guide walls forthe track.
 20. The robot of claim 18 in which the magnet modules includeat least one permanent magnet sandwiched between a flux return backerand an intensifier pole piece.
 21. The robot of claim 18 in which themagnet module includes a head portion received in the slotted frame. 22.The robot of claim 18 in which further including a spring between theslotted frame and the head portion.
 23. The robot of claim 18 in whichthe slotted frame includes a top guide rail for the track.
 24. The robotof claim 18 in which the track includes slats coupled to a chain. 25.The robot of claim 24 in which the slats include discontinuities toprevent shunting.